More specifically, the present invention relates to an electric motor of the type comprising, in a manner known per se, a stator and a rotor, in which the rotor in turn comprises a cylindrical driving shaft mounted so as to be rotatable in the stator and a bowl-shaped metal case having a lateral skirt wall which extends around the stator, and having a bottom wall in which there is constructed a tubular fixing formation through which the shaft extends and which is fixed to the shaft.
FIG. 1 of the appended drawings partially and schematically illustrates an electric motor M of this type, constructed according to the prior art. Motor M comprises a stator S which is illustrated with broken lines, and a surrounding rotor R. Rotor R comprises a cylindrical driving shaft 1 which is mounted so as to be rotatable in the stator S with interposition of bearings 2 of a type known per se. The rotor R further comprises a substantially bowl-shaped metal case 3 having a lateral skirt wall 3a which extends around the stator and carries permanent magnets 4, and having a bottom wall 3b in which there is provided a tubular central fixing formation 5 which is directed towards the stator S, by means of drawing. The tubular formation of the case 3 is fixed to the shaft 1, for example, by means of an interference fit.
The use of electric motors according to the prior art of the type set out above with reference to FIG. 1 involves problems connected with the concentration of the loads in the central region of the case of the rotor, in particular in the region immediately surrounding the tubular formation by means of which the case is fixed to the driving shaft.
Hence there is a desire for a solution which allows those disadvantages of the motors according to the prior art to be overcome.